1. Field of the Invention:
Offset printing presses, including web-fed presses, in which a web of paper is printed, and sheet-fed printing presses, through which individual sheets are conveyed to be printed in colors on one side or on both sides, include multiple printing units. Each printing unit includes an inking unit, and each inking unit includes an ink fountain extending over a width of a printing format. The ink fountain is in contact with an ink fountain roller, which takes up the ink to be applied from the ink fountain and conveys it to further rollers of the inking unit. If the printing press includes a so-called short inking unit, anilox ink that it uses is contained in a chambered doctor blade, which is in engagement with a screen roller that functions similarly to the ink fountain roller.
From print job to print job, it may be necessary to change the ink in the respective inking unit and in the respective ink fountain. Such a necessity may arise because the next job is printed with a different set of inks or because the properties of the ink no longer meet the requirements, for instance in terms of its degree of contamination or the like. In general, a job change consequently requires the ink fountains to be emptied and the entire inking unit, the blanket on the blanket cylinder and the impression cylinder, i.e. all of the parts that received ink during the printing operation, to be washed.
Washing devices for lithographic offset printing presses are described, for instance, in the following documents: U.S. Pat. Nos. 8,056,476 B2, 8,033,219 B2, 7,677,174 B2, 7,533,609 B2 and 7,373,882 B2.
Such a job change thus incurs considerable down-time of the machine. That is not exclusively due to the cleaning operations, but they significantly contribute to the down-time.
Many attempts have been made to reduce make-ready times of lithographic offset printing presses with special emphasis on shortening the washing times. One attempt was to run all washing programs for all printing units of the printing press at the same time. Such a parallel sequence is the current way of controlling the washing operation. It has also been proposed to carry out washing operations while the printing plates are being changed for the next job. Yet for that purpose, it is necessary, for example, to decouple the plate cylinder from the gear train for the individual cylinders of the printing press in order to be able to drive/move it separately to carry out the plate change while a washing operation is carried out on the blanket cylinder, during which the latter is subject to a different sequence of motions.
European Patent Application EP 0 654 350 B1, corresponding to U.S. Pat. No. 6,109,182, proposes to provide variable washing sequence programs depending, for example, on the course of time, on operating parameters of the printing press, or on the degree of contamination. For that purpose, European Patent EP 0 654 350 B1, corresponding to U.S. Pat. No. 6,109,182, relies on washing sequence programs that run in a fully automated way and are completely without any option for operator intervention.
However, those approaches that attempt to optimize make-ready times exclusively by influencing the washing program or the washing times themselves are too short-sighted, for there are many other operations, including manual ones, that a press operator needs to carry out on a printing press during a job change. One of them is to empty the ink fountains, a manual process that requires the ink fountains to be “troweled off” or scraped off. In the process, a foil that had been placed in the ink fountain or ink trough is removed with the residual ink, and the side walls, which laterally delimit the ink fountain and seal it towards the ink fountain roller, are cleaned. The process also involves the reintroduction of a new foil and the refilling of the ink fountain with new ink, a process that may be done by hand using an ink trowel or by inserting a suitable new ink cartridge into an automated refill system that slides back and forth above the ink fountain to fill the latter and to re-meter the ink when necessary.